Removal of Nitrate from Groundwater by Anoxic Biological Reactor

Abstract

Groundwater pollution by nitrate is considered as an important problem that must be addressed because many of the populations experiencing a big shortage of drinking water. In this study, the anoxic biological reactor is used to remove nitrates from groundwater. In this reactor, bacteria convert nitrate to nitrogen under anoxic conditions and lack of availability of nutrients to get the necessary energy. Five types of membrane bio-pregnant carrier within the reactor namely: activated carbon (1- 3 mm), granules of polyethylene (thickness of 3 mm X 4 mm Dia.), bentonite (0.5-1 mm), red wood (2X2X2 cm) and black sand (0.6 – 1.2 mm) are employed. Four types nutrients namely: Four types of carbonate which are: ethanol, molasses, glucose and acetic acid with the addition of sodium ortho phosphate dihydrogen (NaH2PO4) are used. Laboratory results showed that the use of activated carbon gave the best results with respect to the removal of nitrates. The results indicated also that acetic acid and molasses are the best nutrients for the reduction of nitrate ions. However, molasses may cause deposits on the inside walls of pipes and pumps. The removal efficiency of nitrate reached to 92% when using molasses and reached to 99.7% for acetic acid while it reached 54% when using glucose.